Polycarbonate has found many uses because, in general, it combines a high level of heat resistance and dimensional stability with good insulating and non-corrosive properties, and it is easily molded. However, its ductility is often reduced by contact with organic solvents such as gasoline. In blends of polycarbonate with other polymers such as polyester, especially in those blends also modified with an epoxide-containing copolymer, a balance of properties is consequently sought for the purpose of arriving at a useful level of both impact and solvent resistance.
References are known which disclose compositions of polycarbonate, polyester, an epoxide-containing copolymer modifier and a rubber-modified styrene/acrylonitrile copolymer. Among these are Akagi, JP 62-184,051, which discloses a 5-component system such as compositions containing polyester, polycarbonate, butadiene-based graft copolymer, ethylenic copolymer, and glycidyl ester copolymers. Other references such as Taubitz, U.S. Pat. No. 4,774,286; Lausberg, U.S. Pat. No. 4,912,163; and Chung U.S. Pat. No. 4,554,315 disclose a 4-component system of polyester, polycarbonate, butadiene-based graft copolymer, and glycidyl ester copolymers, but describe a butadiene-based graft copolymer, as a component therein, as having greater than 25 percent rubber by weight.
It has been found, however, that the use a rubber-modified sytrene/acrylonitrile copolymer which contains 1-25 percent rubber by weight in a blend of polycarbonate, polyester and an epoxide-containing modifier results in a composition which, when molded, possesses a good balance of processing and physical properties, for example a desirably high level of solvent and impact resistance. This is surprisingly accomplished at a relatively low rubber content and without the use of impact modifiers other than the rubber-modified sytrene/acrylonitrile copolymer.